Gas turbine engines are used to power aircraft, watercraft, power generators, and the like. Gas turbine engines typically include a compressor, a combustor, and a turbine. The compressor compresses air drawn into the engine and delivers high pressure air to the combustor. In the combustor, fuel is mixed with the high pressure air and is ignited. Products of the combustion reaction in the combustor are directed into the turbine where work is extracted to drive the compressor and, sometimes, an output shaft, fan, or propeller. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.
Turbines typically include alternating stages of static vane assemblies and rotating wheel assemblies. The rotating wheel assemblies include disks carrying blades that are coupled to the disks. When the rotating wheel assemblies turn, tips of the blades move along blade tracks included in static shrouds that are supported around the rotating wheel assemblies.
Interest in improving efficiency and reducing emissions of gas turbine engines is driving demand for closer tolerances in the operation of gas turbine engines. For example, the efficiency of a gas turbine engine is improved when flow paths that allow combustion products to pass through the engine without having work extracted from the combustion products is reduced. One area where combustion products can pass without having work extracted is between the blades and surrounding blade tracks.